SXT Status Report
               10 February 1997 to 24 February 1997
                           (Weeks 7-8)

                       H. Hudson, N. Nitta 

       

SUMMARY

SXT continued to operate well, and activity was generally low.
Perturbations to the SXT operations due to HALCA activity have
diminished.

SOLAR ACTIVITY

Solar activity picked up towards the end of the week, with some
C-class flares (largely at orbit night for Yohkoh, of course!) and
an LDE, apparently from either a new-cycle region or the N polar
crown.

SXT INSTRUMENT STATUS

SXT continues to perform well.

SXT CALIBRATION ACTIVITIES

Good news - SXT passed a milestone on the 19th, when it completed a
complete survey of all filter combinations for the stray-light
correction program. This took almost six months to complete, but this
is the first time we have succeeded with this difficult operation.
We can now focus on more specific topics.

The HXT calibration issue possibly related to the long SXT bakeout,
reported in the last status report, has now been resolved.  It does not
appear now that the bakeout procedure has any appreciable effect
elsewhere in Yohkoh.

PASS CONFLICTS

Telemetry contact passes continue to be lost to HALCA operations, but
not so many: 

Week 7:  only 11 passes (out of a normal ~30) could be used!
Week 8:  12 cancellations (19 total).

During this period NASA covered some of the missing orbits via
Santiago and DSN coverage, for which we are grateful.

CAMPAIGNS

There were two campaigns during this reporting period: one day was
spent in ARS0 looking at a filament at south central meridian, for
which SOHO CDS and Sumer could also observe; and two days were spent
looking at the ingress and egress trajectories of NEAR. Richard Woo of JPL
is using its telemetry signals for IPS observations of the corona down
to maybe 1.2 solar radii. The SXT definition of the coronal structures
is an important part of interpreting the scintillations. Woo was lucky
to have had some activity on the right limb during the NEAR egress, so
he will have both quiet Sun and active Sun in the records.

For Yohkoh target planning, the SXT weekly observing plan is available
on the Web at 
	http://www.space.lockheed.com/SXT/html2/First_Light.html 
or with
	"finger campaign@isass0.solar.isas.ac.jp | more"	.

See 	http://sohowww.nascom.nasa.gov/operations/targets/today" 
for SoHO target planning. 


VISITORS AND PERSONNEL

R. Schwartz visited from GSFC.  Sam Freeland came and went, after
installing SolarSoft.  Nariaki Nitta returned to California.  Jim Lemen
and Tom Metcalf arrived, and Serge Savy returned.


SEMINARS

N. Shimada (Tokyo) "Particle acceleration in slow shocks"

T. Naito (Tokyo), "Particle acceleration in shock waves with 
  oblique magnetic fields"

This concludes our series of seminars on shock waves and particle
acceleration. Alas, although these were all interesting presentations,
it is clear that a lot of understanding still remains to be hoped
for.

Week 7 Tohbans

SSOC: M. Nishio, Y. Suematsu & M. Saito 
KSC:  H. Tonooka & S. Akiyama 
SXT CO:   N. Nitta
Software: G. Slater, S. Freeland

Week 8 Tohbans

SSOC: A. Okubo & K. Akita 
KSC:  S. Akiyama & H. Sekiguchi 
SXT CO:  H. Hudson 
Software: G. Slater


QUOTATION (Y. Berra) 

"When you come to a fork in the road, TAKE IT!"